Disposable low-melt thermoplastic mask incorporating an intergral locking mechanism for attachment to patient restraint boards

ABSTRACT

A disposable mask system for positioning a patient relative to a patient restraint board during radiation therapy includes a piece of low-melt thermoplastic material affixed to a rigid, non-thermoplastic frame. A lock-down mechanism is integrally incorporated into the rigid, non-thermoplastic frame, such that a manipulable portion of the lock-down mechanism extends upward from the surface of the rigid frame so that it is accessible by the user. An engagement member extends downward from the underside of the rigid frame such that it can engage corresponding holes in a patient restraint board, such that when the rigid frame is pushed down so that its engagement members fully engage the corresponding holes of the patient restraint board, then the thermoplastic mask system may by tightly secured to the patient restraint board by activating the lock-down mechanism.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of pending application Ser.No. 10/924,547 filed Aug. 24, 2004, which claimed the benefit, under 35U.S.C. § 119(e), of the provisional application filed Aug. 25, 2003under 35 U.S.C. § 111(b), which was granted Ser. No. 60/497,618. Bothapplications are hereby incorporated by reference in their entireties.

BACKGROUND OF THE INVENTION

Cancer treatment using external beam radiation therapy is a common andgrowing method of treatment for patients with many kinds of cancers. Inalmost all of these patients, cancerous tissue lies adjacent to healthytissue, which often contains important organs, nerves, and otherstructures that can be exquisitely sensitive to radiation injury.Therefore, during the course of treatment great care must be taken tospare normal tissue and only irradiate the cancerous tissue.

The treatment process using external beam radiation therapy is complexand exacting. It almost always entails multiple treatments given overseveral weeks to complete the course of therapy. Because of this, thepatient must be positioned and re-positioned accurately for eachradiation therapy treatment to ensure that the proper radiation dose isdelivered only to diseased tissue, and to spare the normal tissue asmuch as possible.

To this end, a number of devices have been developed to ensure the exactpositioning of the patient. Many of these positioning devices rely onthe use of a form-fitting low-melt thermoplastic “mask” of the patient'shead, head and shoulders, or other body anatomy to hold the patient inexactly the same position time after time, thus ensuring that there isno patient movement during the treatment process.

The use of such devices has become commonplace in the industry. They areconsidered “disposable”, i.e., intended for single patient use only, andare meant to be discarded after the patient completes their course oftherapy. They are formed of an injection molded, non-thermoplastic framebonded to the sheet of low-melt thermoplastic. The form-fitting mask istypically made by heating the low-melt thermoplastic in a water bathuntil the material becomes pliable. It is then removed from the waterbath, and then draped over the patient's face or torso and pressed toconform tightly to the patient's anatomy. As the material cools, itagain becomes stiff and rigid, and thereby immobilizes the patient forhis/her course of radiation therapy.

A common complaint with patients treated in this manner is that theset-up time, i.e. the time required to position the patient accuratelyfor treatment is time consuming and thus costly. It is thereforedesirable to speed up and simplify the set-up process to increasetreatment accuracy and patient throughput.

All current disposable low-melt thermoplastic masks must be locked downto the patent restraint system being used via some form of clampingmechanism. Current devices utilize screw-down clamps and other similardevices to affix the mask to the restraint board. Some other systems usea non-disposable holder into which the disposable thermoplastic mask isplaced and secured, either by screw-clamps or “snap fit” mechanisms;this holder is then clamped to the restraint board using mechanismssimilar to those described above.

In all of these cases the thermoplastic mask itself does not possess anymechanism that allows it to be easily and securely affixed to thetreatment board. All must be attached to the treatment board in alaborious and time-consuming fashion, requiring several radiationtechnologists (those folks responsible for patient setup) be involved inthe set-up process.

BRIEF SUMMARY OF THE INVENTION

This invention relates to an improvement over the standard head or headand shoulder low-melt thermoplastic mask that simplifies patient set-up,reduces set-up time, and provides for a more efficient treatmentprocess.

The invention incorporates a unique locking system directly into therigid frame surrounding the piece of low-melt thermoplastic. This allowsthe frame to be locked down onto the patient restraint device directlyand easily, eliminating the need for cumbersome clamping mechanismswhich can prolong set-up times, frustrate techs, and may lead totreatment inaccuracy as the lock down mechanisms wear and shift withtime and use. No other current disposable low-melt thermoplastic framesincorporate such a mechanism into its construction.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages of the invention will become readily apparent to thoseskilled in the art from the following detailed description of variousembodiments when considered in the light of the accompanying drawings,in which:

FIG. 1 is a partial, isometric view of the invention in its “unlocked”position and positioned above a patient restraint board;

FIG. 2 is an enlarged side view of a portion of the inventionillustrated in FIG. 1 in its “locked” position;

FIG. 3 is a top isometric view of the invention without a locking pin inplace;

FIG. 4 is a bottom isometric view of the invention without the lockingpin in place;

FIG. 5 is a cut-away isometric view of a portion of the inventionwithout the locking pin in place;

FIG. 6 is an isometric view of the locking pin only;

FIG. 7 is a side view of an alternative embodiment of the lockingmechanism in accordance of the invention;

FIG. 8 is a top view of the entire rigid, non-thermoplastic frame inaccordance with the invention;

FIG. 9 is an isometric view of the entire rigid, non-thermoplastic frameshown in FIG. 8; and

FIG. 10 shows an isometric view of the underside of the rigid,non-thermoplastic frame shown in FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

It is to be understood that the specific devices and processesillustrated in the attached drawings and described in the followingdescription are simply exemplary embodiments of the inventive conceptsdefined in the appended claims. Hence, specific dimensions and otherphysical characteristics relating to the embodiments disclosed hereinshould not be considered as limiting, unless the claims expressly stateotherwise.

The invention relates to a thermoplastic mask system comprised of asheet of die-cut low-melt thermoplastic bonded or glued or otherwisesecured to a rigid, non-thermoplastic frame, usually in a U-shape orother configuration. The low-melt thermoplastic material has specificproperties; i.e., when it reaches a specific temperature thethermoplastic softens and becomes extremely pliable, allowing thematerial to be stretched over a patient's head or other body part,conforming tightly to the patient's anatomy. As it cools, thethermoplastic becomes rigid again, and holds the shape to which it hasbeen conformed. In this way, the thermoplastic forms a mask that tightlyconforms to the patient's unique anatomical shape. The rigid,non-thermoplastic frame serves as a handle to allow the radiationtechnologist to manipulate the pliable, warm thermoplastic, and helpsthe technologist to stretch the warm pliable material over the patient'sanatomy. The thermoplastic mask, once formed, cannot be easily re-formedto fit another patient. Thus, it is intended for single patient use, andis meant to be disposable after completing the patient's course oftherapy.

The current invention incorporates a simple locking mechanism directlyinto the frame of a thermoplastic mask, making the device able to belocked-down to a patient restraint board without the use of accessoryclamping mechanisms. This modification to existing technologyfacilitates the use of the thermoplastic mask by enhancing both thespeed and accuracy by which a thermoplastic mask of a patient's anatomymay be made. In current designs, two or more radiation technologists arerequired to form the mask, one to push the pliable warm thermoplasticover the patient's face or torso, and another to position and tightenthe clamping mechanism. Incorporating the locking mechanism directlyinto the frame of the thermoplastic mask makes it possible for a singleradiation technologist to form the frame over the patient and lock itsecurely to the restraint board until it cools to rigidity.

The locking mechanism may take several forms. In the preferredembodiment, the locking mechanism includes a rotating cam-like mechanismthat functions to draw closer or extend a locking pin closer-to orfurther-from the rigid, non-thermoplastic frame. The locking pin has anexpander at its tip that engages a split expandable member on theunderside of the frame. When the locking mechanism is rotated from the“open” to “locked” position, the locking pin is pulled tighter to theframe forcing the expander at its tip to engage and expand theexpandable member on the underside of the frame.

In use, the warm, pliable thermoplastic is forced down over the patient,conforming to his/her anatomy. The locking mechanism is in the “open”position. The expander members on the underside of the rigidnon-thermoplastic frame mate with corresponding holes in the restraintboard that have a reverse frusto-conical shape to them. When thethermoplastic is fully conformed to the patient's anatomy and theexpander members on the underside of the rigid frame are fully engagedinto the corresponding holes in the restraint board, the locking cam isrotated to the “locked” position. This forces the expandable members toexpand and tightly engage the restraint board, holding the finishedthermoplastic mask securely in place.

Other forms of integral locking mechanisms are possible, including avariation of the preferred embodiment utilizing a panel rivet-likemechanism to expand the expandable member on the underside of the rigidframe. Still other forms may be envisioned using other cam-mechanismsand other means of expanding the expandable member. Still otherembodiments may use a “lock and key” mechanism utilizing mating shapesof the hole in the restraint board and the member extending from theunderside of the thermoplastic mask frame. Still other embodiments mayutilize spring-loaded or similar mechanisms to engage suitably designedposts or similar members extending upward from the restraint board.

Other mechanisms may also be envisioned which meet the intent ofincorporating the lock-down mechanism directly into the rigid frame of adisposable thermoplastic mask system. One such example is a latchingmechanism utilizing a locking means extending downward from theunderside of the rigid frame of the thermoplastic mask that mates withan undercut in the patient restraint board, such that when the rigidframe is pushed down onto the patient restraint board a ridge on thelocking member engages the undercut in the restraint board in a securemanner, securing the thermoplastic mask system to the patient restraintboard. A release mechanism is provided by a member extending upward fromthe rigid frame such that when the user squeezes or laterally moves therelease member the locking means is levered laterally, releasing theengagement of the locking means and the undercut in the patientrestraint board.

Referring now to the drawings, FIG. 1 shows an isometric view of thecurrent invention in its “unlocked” position. In its preferredembodiment, the locking mechanism comprises a rotating cam-likemechanism that functions to draw closer or extend a locking pincloser-to or further-from the rigid, non-thermoplastic frame 6. Thelocking pin 1 has an expander at its tip 2 that engages a splitexpandable member 3 on the underside of the frame 6. A notched collar 5and the split expandable member 3 are both integral parts of the frame6. A plurality of these locking mechanisms are arrayed about theperiphery of the frame 6 in sufficient number so as to securely lock theframe 6 to the patient restraint board 8 when the locking mechanism hasbeen engaged.

When the locking pin is rotated from the “unlocked” to “locked”position, the cross-piece 4 at the top of the locking pin 1 engages thenotched collar 5 on the top surface of the frame 6. This produces acam-like action on the cross-piece that forces the locking pin upwards,causing the locking pin 1 to be pulled tighter to the frame 6. This inturn forces the expander at its tip 2 to engage and expand theexpandable member 3 on the underside of the frame 6. A portion of thepatient restraint board 8 with its corresponding hole 7 that mates tothe locking pin 1 is also shown in FIG. 1.

FIG. 2 illustrates in the invention in its “locked” position. In thisview, the cross-piece 4 has been rotated 90 degrees, engaging thenotched collar 5 as described, with the resulting cam-like actionforcing the locking pin 1 upwards. In this figure, the expander at thetip of the locking pin 2 is shown as having engaged and expanded theexpandable member 3 on the underside of the frame 6. The expandedexpandable member on the underside of the frame is shown having engagedthe corresponding hole in the patient restraint board, thereby lockingthe device securely to the patient restraint board.

In the preferred embodiment illustrated in FIG. 3, the notched collar 5is clearly depicted and is seen to be an integral part of the frame 6.The expandable member 3 is shown on the underside of the frame, and isalso an integral part of the frame 6.

The underside of the frame 6, best seen in FIG. 4, is shown having a“shelled-out” structure 12 that decreases the radiation attenuation ofthe frame. The expandable member 3 is also shown in FIG. 4 as anintegral part of the underside of the frame 6.

FIG. 5 provides a clear view of the frame without the locking pin inplace. A lip 10 is preferably formed in the interior of the expandablemember 3. When inserted into the locking mechanism and the device is inthe “unlocked” position, the expander tip extends beyond the tip of theexpandable member. When the device is in the “locked” position, theexpander tip is pulled upward and seats on the face of the lip 10,forcing the expandable member to flare outward and “locking” orselectively securing the device to the patient restraint board 8.

FIG. 6 shows the locking pin 1 only. In its preferred embodiment, thelocking pin has a T-shaped configuration, with the cross-piece 4 at thetop and the expander tip 2 at the bottom. In use, the locking pin 1 ismated to the locking mechanism by inserting it into the notched collarand pushing until it seats in the recess in the inside of the expandablemember. Alternate embodiments are possible that include modifications indesign of the cross-piece and the expander tip.

An alternate embodiment of the locking mechanism is shown in FIG. 7.Again seen is the locking pin 1′, shown in an alternate configuration.The expandable member 3 is seen as before, and is an integral part ofthe frame 6, as before. The notched collar is not depicted because ithas no function in this embodiment, and is therefore omitted. In thisembodiment, the device functions in the same fashion as a panel rivet.When the locking pin is in its “unlocked” position, the expander tipseats within the recess in the expandable member 3, as above. When thelocking pin 1′ is depressed, the expander tip 2′ forces the expandablemember to expand, thereby selectively locking the device to the patientrestraint board.

FIG. 8 illustrates an entire rigid, non-thermoplastic frame 6. Theoutline is configured to match commercially available patient restraintboards. It is understood that this configuration may be changed to matchother commercially available boards. In the preferred embodiment, aplurality of locking mechanisms are arrayed along the length of theframe 6 in sufficient number so as to securely lock the frame 6 to thepatient restraint board when the locking mechanism has been engaged. Inthis figure, the locking mechanisms are shown in their assembled,ready-to-use form. The locking pin cross-pieces 4 can be seen resting intheir respective notched collars 5. In this view, cross-pieces orientedparallel to the linear axis of the frame will be in the “unlocked”position (as shown at numeral 11), whereas cross-pieces orientedperpendicular to the linear axis of the frame will be in the “locked”position (as shown at numeral 12).

Referring to FIG. 9, the T-shape of the locking pin 1 is shown, againwith the cross-piece 4 resting in the notched collar 5. Also in thisview is seen the expandable member 3 on the underside of the frame 6,with the expander tip 2 of the locking pin 1 visible. Again, some of thelocking mechanisms are shown in the “un-locked” position, and some areshown in the “locked” position.

From the underside of the rigid, non-thermoplastic frame 6 shown in FIG.10, the “shelled-out” structure 12 of the frame is seen. The slottedexpandable members 3 of the locking mechanisms are seen, and are anintegral part of the frame. The expander tip 2 of the locking pin 1 canbe seen protruding just past the expandable member 3. Again, thecross-pieces 4 of several locking pins are shown, some in the “locked”and some in their “unlocked” position.

In accordance with the provisions of the patent statutes, the inventionhas been described in what is considered to represent its preferredembodiments. However, it should be noted that the invention could bepracticed otherwise than as specifically illustrated and describedwithout departing from its spirit or scope. As an example, it will beappreciated that, in those embodiments in which the apparatus includes aplurality of projections, the size and shape of the projections may varyconsiderably.

1. A method of securing a mask system, comprised of a piece of low-meltthermoplastic material affixed to a rigid, non-thermoplastic frame, to apatient restraint board utilizing a lock-down mechanism integrallyincorporated into the rigid, non-thermoplastic frame.
 2. The method ofclaim 1, wherein the lock-down mechanism is comprised of a rotatingcam-like mechanism.
 3. The method of claim 1, wherein the lock-downmechanism is comprised of a panel rivet design.
 4. The method of claim1, wherein the lock-down mechanism is comprised of a locking meansextending downward from the underside of the rigid frame of thethermoplastic mask that mates with an undercut in the patient restraintboard.
 5. A disposable mask system comprised of a piece of low-meltthermoplastic material affixed to a rigid, non-thermoplastic frame,wherein a lock-down mechanism is integrally incorporated into the rigid,non-thermoplastic frame for selectively securing the mask system to apatient restraint board.
 6. The method of claim 1, wherein the lock-downmechanism is comprised of a rotating cam-like mechanism that functionsto draw closer or extend a locking pin closer-to or further-from therigid, non-thermoplastic frame, and the locking pin has an expander thatengages a split expandable member on the underside of the frame, whereinwhen the locking mechanism is rotated from the open to locked position,the locking pin is pulled tighter to the frame forcing the expander toengage and expand the expandable member on the underside of the frame.7. The method of claim 1, wherein the lock-down mechanism is comprisedof a panel rivet design, such that depressing the head of a plurality ofpanel rivets extending upward from the surface of the rigid frame forcesexpansion of corresponding expandable members on the underside of therigid frame, and when the expandable members on the underside of therigid frame are fully engaged into the corresponding holes in therestraint board, then the expansion of the expandable members on theunderside of the rigid frame securely engages the finished thermoplasticmask in place on the patient restraint board.
 8. The method of claim 1,wherein the lock-down mechanism comprises a plurality of splitexpandable members integrally formed with and extending downward fromthe underside of the frame and being adapted to engage correspondingholes in the patient restraint board and a plurality of panel rivets,each panel rivet cooperating with a corresponding one of the splitexpandable members and having a manipulable portion extending upwardfrom the surface of the rigid frame so that it is accessible by a user,and wherein each panel rivet is depressed to force expansion of thecorresponding split expandable member on the underside of the rigidframe to securely the thermoplastic material in place on the patientrestraint board.